Detrital Zircons from Severnaya Well (Franz Josef Land, Arctic): Insights into Triassic Palaeogeographic Reconstructions

Alex Soloviev

Detrital zircon morphology and U/Pb LA-ICPMS age data (4 sample, 100 grains per sample) from Triassic sandstones collected from the Severnaya well cores (Graham Bell Is, NE part of the Franz Josef Land) were used to investigate provenance changes with time, constrain source areas and test paleogeographic reconstructions for the Triassic. The zircon ages (370-270 Ma) from the Middle Triassic (Upper Anisian) sample suggest that the main source of clastic material was the Uralian fold belt or the Polar Urals and Novaya Zemlya. A second source shed sediments into the basin and this source is characterized by Neoproterozoic zircons (800-560 Ma). The provenance was probably eastern front of the Urals or/and the northern and central zones of Taimyr. The clastic material was transported to the basin from the S and SE. The Siberian plume and associated volcanism gave the young zircons (270-240 Ma) in the Mid Triassic (Upper Ladinian) sample. The Uralian (360–270 Ma) and the Neoproterozoic (840-540 Ma) sources remain the dominant sources, but their influence is diminished as sediment transport from the Caledonian orogen increases. Zircons from the Caledonian orogen (500-440 Ma) could be related to erosion to the east (Severnaya Zemlya) or to the west (Svalbard). At the same time, Paleoproterozoic (1.6-1.8 Ga) and Mesoproterozoic (1.4-1.5 Ga) sources appear. The provenances for these zircons could be Laurentia in the NW or Baltica in the SW. Baltica is preferred because it has 1.48-1.64 Ma while Laurentia does not. The Upper Carnian sample showed that the erosion of the Siberian Traps and younger volcanics (270-220 Ma), Uralian (370-270 Ma) and Caledonian (390-480 Ma) sources increases again in the beginning of the Late Triassic while the zircons from Paleo-, Meso- and Neoproterozoic sources nearly disappear at the same time. The Upper Norian sample documents that the influence of sediment sources from the Siberian Traps and younger volcanics (270-220 Ma), Uralian (370-270 Ma) region becomes less significant in the end of the Triassic. The clastic transport increases from Caledonian (500-390 Ma) sources as well as from Paleo-, Meso- and Neoproterozoic rocks. The main source for the Middle to Late Triassic sediments was the Uralian orogenic belt (Polar Urals, Novaya Zemlya). The influence of Neoproterozoic sources systematically decreases and Caledonian sources increase from the Middle to Late Triassic. We can conclude that sediments from Uralides reached Franz Josef Land at least in the Middle Triassic and thus earlier than they reached Svalbard in Late Triassic (Riis et al., 2008; Bue et al., 2011). The regional depositional system represented by the subsurface stratigraphy of Franz Josef Land was linked to the North Barents Sea basin in Middle and Late Triassic time. We do not see good evidence for linking the depositional system in Franz Josef Land with that represented by the Svedrup Basin at the same time. The study was supported by NPD and CALE.

AAPG Search and Discovery Article #90177©3P Arctic, Polar Petroleum Potential Conference & Exhibition, Stavanger, Norway, October 15-18, 2013